High Idle, Rough Starts and stalling engine

Foxy87 · Post by **Foxy87** » 18 Jul 2011, 21:46

Hi,
I have a 1987 Volvo 240 station wagon and I've been having some engine problems. It started last summer when it started to have a really fast idle. I shut the car off to stop the high idle and it wouldn't start again after that. It tried starting and turned over until it would start really rough and the whole car would shake and dark smoke would come out of the exhaust until it would sputter to a stop. Later I realized if I rev it up the shaking goes away and it can be driven normally. I then put seafoam in the tank and the problem happened less frequently until after a couple weeks, it appeared to have fixed itself. I drove it the rest of the year and had no problems until recently. Occasionally it would idle higher than normal but it would always go away and slow back down. Earlier this summer, it would always die after I shifted into gear when I first started it. I realized that if I rev it up before shifting, then it is able stay running when I shift into drive or reverse. A couple days after that problem it started doing the high idle and occasionally the rough starts and dark exhaust. It only does the rough starts and smoke when its idling fast so I think it is related to the engine flooding from the fast idle. So if I'm able to fix the fast idle, I think it will be fixed. I've put Lucas Oil into my last four or five tanks. It has helped a lot and pretty much eliminated the rough starts but it still has the fast idle. I can get up to 30mph without pressing the accelerator and when I shift into park or nuetral, it sounds like it idles at about 1300 rpms but thats just a guess. I think I will add seafoam again to see if that fixes the problem but I want to fix it right and eliminate this problem permanently. Last summer I took apart the throttle body and cleaned it out thoroughly so I don't know what what to do next. I think I might clean out the mass air flow meter next but does anyone have any ideas?
Thanks in advance for the help

Post by **jimmy57** » 18 Jul 2011, 22:55

The engine coolant temp sensor or its connector are the most likely problems. Ground to engine from battery and to chassis from battery also can be the cause.
The normal routine is for increasingly colder temps to give you an increasingly faster idle speed at start that is accompanied by increasingly richer fuel mixture. If you start it at 75 F and it is signalled 15F you will have a really high idle and it will flood and put out black smoke as the extra fuel is not needed for the warmer temp.
The ECT sensor on that engine is just behind the third intake port on cylinder head. Be sure you get the correct sensor. 89-93 240's use a sensor that will plug in but it will give you the same symptoms as a bad sensor.

Has your fuel economy been really bad since this started?

Other things can cause similar symptoms like MAF sensor but that doesn't give high idle also.
Mis-adjusted throttle can give high idle but not the rough running that sounds like over-rich fuel mixture. I am thinking the hard to start after you shut it off is over-rich. The engine can take the extra fuel when you start it after it sits for a couple of hours or longer but if it is already warmed up the extra fuel will flood engine easily at start.

Foxy87 · Post by **Foxy87** » 19 Jul 2011, 21:54

My car speedometer is 3-5 mph slow depending on how fast I'm going. So i figure that means my odometer is off by about 2 miles every 20. I've been getting about 24 mpg but that is probably closer to 22. I do mostly freeway driving though so even if its idling high, I'm pressing on the gas pedal to make it stay up to speed. So if the engine coolant temp sensor or its connector is the problem, would it make sense that Seafoam could fix it for 9 months and then the problem would start again? I should probably mention that this problem started again when I put some old gas in my car. Another thing that I don't think is related but I'll mention anyways is that if I take it on a long drive, sometimes the temperature gauge on my dash goes down all the way, as if the car was off. But for most drives, it warms up and stays in the normal range. Is the coolant temp sensor a cheap part? Should I order online or go to a junk yard? Is there way to test it (continuity test?) before buying a replacement?
Thanks

ruvyrk · Post by **ruvyrk** » 03 Aug 2011, 21:30

hi i have an 86 240 that has part of these problems which is that when i start the car it keeps stalling out unless i race the engine while i put it into gear this problem was much worse in the winter also the temp gauge is all whacked out it will show the car is overheating as soon as i start and then whill go to the middle could these two be related?